CAPITAL STOCK AND SHARE-BASED COMPENSATION - Employee Stock Purchase Plan Purchases (Details) - $ / shares	3 Months Ended								55 Months Ended	79 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employee Stock Purchase Plan shares issued (shares)	7,856	6,052	8,673	10,913	13,323	12,276	11,446	13,244	3,039,200	3,122,983
Price per Employee Stock Purchase Plan share issued (usd per share)	$ 99.54	$ 106.22	$ 72.64	$ 51.29	$ 44.80	$ 47.57	$ 53.39	$ 43.43	$ 14.72	$ 99.54